Electrical measuring instrument.



M. J, WOHL da H. HBRTZBERG.

ELECTRICAL MEASURING INSTRUMENT.

APMIOATION FILED MAR. zo, 1908.

Patented Ma 1910.

UNITED sT-ATEs PATENT oEEioE.

MAURICE J'. WOHL, OF NEW YORK, ANI) HARRY HERTZBERG, OF BROOKLYN, NEWYORK, ASSIGNORS TO ABBOT A. LOW, OF HORSESHOE, NEW YORK, MAURICE J.WOHL, OF NEW YORK, N. Y., AND HARRY HERTZBERG, OF BROOKLYN, NEW YORK,

TRUSTEES.

ELECTRICAL MEASURING INSTRUMENT.

Tc all whom it may concer/n:

Be it known that we, MAURICE J. WOHL and HARRY HERTZBERG, citizens ofthe United States, and residents, respectively, of the city of New York,borough of Manhattan, county and" State of New York, and of the city ofNew York, borough of Brooklyn, county of Kings, and State ofV New York,have invented certain new and useful Improvements in ElectricalMeasuring Instruments, of which the following is a specication.

This invention relates to electrical measuring instruments, moreparticularly adapted for registering the maximum currentI Howing in acircuit.

roadly, the invention consists in a circuit, a resistance-heatedthermostat operated by the circuit, a movable indicator, and connectionbetween the thermostat and indicator whereby the latter is actuated onlythrough the expansion of the thermostat.

1n the drawings, Figure 1 is a semi-diagrammatic elevation of anapparatus embodying the invention, and Fig. 2 is a partial view similarto Fig. 1, showing a modification.

Referring to these drawings, the numerals 1, 1 indicate a portion of anelectrical circuit, and 2 any suitable casing for the instrument.lieten-ing for the present to Fig. 1, 3 indicates a movable pointer orindicator, pivoted near its upper end to the pivot pin 4 projecting fromthe casing Wall, the pivot aperture 5 of the indicator being slotted, topermit the indicator to move longitudinally. The lower end of theindicator travels over a graduated index plate G, providedwith anarcuate serrated upper edge 7. A paWl or detent 8 secured to theindicator 3 takes into the notches 7, to retain the index end of theindicator in apposition to the several graduations on the plate 6. Thisindicator 3 is shown as being actuated in one direction only by anoperating member in the shape of an arm 9, pivoted toward its lower endat 10 to the casing, and having a projection 11, toward its upper. end,which engages the side of the indicator 3 near the pivot thereof.

It is obvious that movement of the arm 9' toward the right moves theindicator 3 to the right, but that movement of: the arm to Specicationof Letters Patent.

Application led March 20, 1908.

Patented Mar. 1, 1910.

Serial N0. 422,275.

the left does not aii'ect the indicator.

A suitable means for moving the arm 9 in the operative direction isindicated by the weight 12, which is adjustably mounted on the arm 13,rigid with the enlarged hub 14, of insulating material, of the arm 9.

The thermostat, the contraction of which operates to overcome the Weight12 and to move the arm 9 in the inoperative direction, is represented bythe thermal wire 15, which is stretched between spring supports 16, towhich its ends are connected by tension adjusting devices 17. Said wire15 is connected intermediate its length, at 18 and 19, to the hub 14;being, thus, connected to the arm 9 that points at opposite sides of thepivot thereof, whereby contraction of the wire moves the arm 9 to theleft and lifts the weight 12. It is obviously immaterial whether thewire 15 is in one length or two.

The wire 15 is heated by resistance coil 20 connected in 'series in thecircuit 1, 1. But, in order to prevent changes in temperature, due tocauses other than the electrical heating of coil 20, moving the arm 9, acompensating wire 21 is also stretched between the supports 16; its endsbeing connected thereto by tension adjusting devices This wire isadapted to have the same total linear expansion per unit change insurrounding temperature as the wire 15; so that mere changes inatmospheric temperature result only in the wire 21 changing the flexureof the supports 16. Since the amount of change 1n lexure of the supportsis, thus, the saine as the total expansion or contraction of the wire15, the outer ends of this wire sulier displacement under suchconditions, but the points 18 and 19 do not; hence, the arm 9 is notshifted.

The operation will be apparent. The current passing in the circuit heatsthe resistance coil 20, which, in turn, heats the thermal wire 15. Theexpansion of this wire permits the weight 12 to descend, thus moving thearm 9 and the indicator 3. When the maximum current has been reached andthe current begins to diminish, the indicator is held at the graduationrepresenting this maximum, and the contraction of the wire 15, due tothe cooling of the coil 20, lifts the weight 12 and moves the arm 9 inthe inoperative direction. It will be observed that the slotted pivot ofthe indicator 3 permits the latter to reciprocate in ridingalong thenotches 7.

Fig. 2 indicates certain modifications. Here the indicator 3a has aslotted pivotal mounting on the pivot 10 of the hub 14, to

which is secured the weight 12 and weight arm 13. The hub 14; carries apin or projection 22, corresponding in function to the arm 9 in IFig. 1,which engages with the side of the indicator 3a, so as to move thelatter to the right, but not to the left. As indicated, the coil 20 maybe dispensedv with, and the thermostat wire 15a be itself a resistanceelement connected in the circuit. The construction shown in Fig.' 1 ispreferable, in that it provides for a greater movement of the indicatoras the result of. a slight movement of the thermal wire 15, and,moreover, provides for a greater heating eff fect through the coil 20.It will be obvious,

however, `that the two constructions shown are merely illustrative oftheprinciples of the invention, which may be embodied in numerous forms.

V What is claimed as new is:

1. In an electrical measuring instrument, the combination of a movableindicator, an operating member adapted to have operative connection withsaid indicator when moved in one direction only, means adapted throughsaid circuit, said wires having con-l nection with said operating memberand extending therefrom in opposite directions whereby contractionthereof moves said member in the inoperative direction, and means forheating said wires simultaneously by the' current in said circuit.

v2. In an electrical measuring instrument, the combination of a movableindicator, an operating member adapted to have operative connection withsaid indicator when moved in one direction only, means adapted to movesaid member in this direction, a Kpair of thermal wires under tensionconnected with `said operating member, and extending therefrom in oposite directions, said wires being arrange and adapted to operatesimultaneously whereby contraction of `the wires moves said member inthe inoperative direction, and a resistance coil inclosing said wires,said coil being arranged to be con-y nected in the circuit to bemeasured and to thermally affect said wires simultaneously.

3. In an electrical measuring instrument, the combination of, a movableindicator, a pivoted operating member adapted to have operativeconnection with said indicator when moved in one direction only, meansadapted to move said member in this direction, supports positioned onopposite sides of the ivot of said operating member, a pair of tiermalWires, under tension connected to said supports and to saidV pivotedmember at points on opposite sides of the axis thereyof, said wiresbeing arranged and adapted to expand "or contract simultaneously underthermal action, and means whereby said wires are simultaneously heatedelectrically.

4. In an electrical measuring instrument, the combination of a movableindicator, a pivoted operating member adapted to have operativeconnection with said indicator when moved in one direction only, meansadapted to move said member` in this direction, spring supportslpositioned on opposite sides of the pivot of said operating member, apai'r of thermal wires stretched between said supports and saidoperating member at points at opposite sides of the pivoted axisthereof, means whereby said thermal wires are heated and expanded by thecurrent to be measured, and a compensating wire stretched between saidspring supports.V

5. In an electrical measuring instrument, the combination of a movableindicator, a pivoted operating member adapted to have operativeconnection with said indicator when 'moved in one direction only, `meansadapted to move said member in this direction, opposed spring supports,a thermal wire stretched between said supports under tension, beingconnected intermediate its length to said pivoted member at points atopposite sides of the pivotal axis'thereof, whereby contraction of thewire overcomes said means and moves said member in the inoperativedirection, means whereby said wire is heated by the current to beymeasured, and a compensating wire, substantially as described, alsostretched between said spring supports. 1 p

6. In an electrical measuring instrument, the combination of a movableindicator, an operating member adapted to have operative connection withsaid indicator when moved in one direction only, an adjustable weightoperative to move said member in this ,direction, a pair of coperativethermal wires under tension connected with said operating 115 overcomesaid weightand move said member 120 in the' reverse direction whencontracting, and means whereby said wires are heated and expandedsimultaneously by the current yto be measured.

7. In an electrical measuring instrument, ,125

the combination of a circuit, a resistance# heated thermostat operatedby current 1n said clrcuit, a pivoted indicator, connection between saidthermostat and indicator whereby the latter is actuated through theexpan- 1,30

sion, but not through the contraction, of the Kings and State of NewYork, this 18th thermostat, and a rack over which said inday of March,1908.

dicator travels, the indicator having a loose MAURICE J. VOHL.

pivotal mounting whereby it is permitted to HARRY HERTZBERG. 5reciprocate as it passes over the teeth of the Witnesses:

rack. LEWIS W. HASKINS,

Signed at New York in the county of AGEO. WELLING GIDDINGS.

